I personally don't have a problem with it. At some point people are going to figure out a way to get the fastest times possible for boss clears since we gotta farm them for Forge materials. 

Also, these insane speed runs are very very hard to do in the first place- they're champion dependent and gear intensive that I doubt a lot of people could it anyway. So to your point about "finding nice synergy in teams composition and inventing nice tactics"- these speed teams are very well synergized team compositions. :)

I just had a disappointing experience, my team spent about 40 minutes defeating the spider on Floor 70 on DT (normal).  But the game would not register the outcome, I saw where the spider and spiderlings were killed (per info screen) but the game crashed and told me it was "experiencing issues".  All I could do was close the game and go back in to see what I could, but I was not given ctredit for completing that level.  Bummer!!!

SUPPORT wrote back to me upon my query and said there is a 1000 turn limit to avoid overloading the server.  That's BS!!!  If that is the case why doesn't the game crash in mid-stream (at 1000 turns)?? NO, they would rather wait and see the disappointment on your face just when you think you got it beat.

They further said I needed a faster team.  Insult to injury!

Unlike the Clan Boss there is no turn counter on those battles.

Hey, the turn counter is definitely something to watch out for. 

That's mainly the reason why we have a 50 turn limit on CB before he ignores Unkillable and Block Damage buffs. Back then, unkillable teams can go longer but players had to run a timer to approximate the damage and turn count or else the key would be wasted if they reach the 1000 turn limit. 

So unfortunately, support was right. You'd have to beat it with a faster team. 

I have other problem: spider at F90. And it's not only me. It seems like it's one of those bosses that have only one solution and if you don't have that one exact combo of champions you are basically done with the tower. Every other boss can be either brute forced or has a simple(but fun) mechanics. This one just has basically everything and is not fun at all. 

I'm fighting F90 right now.  I'm pat 25 minutes and Miscreated Monster is the only one alive since around 3 minutes. He's slowly wearing the spider down (about 50% right now) but I doubt I'll kill it fast enough.